Variable-speed transmission



3 Sheets-Sheet l W. M. BROBECK VARIABLE-SPEED TRANSMISSION IN VEN TUR.

A WH-UAM M. QOBECK y am.

Feb. 5, 1952 Filed Nov. 24. 1947 Feb. 5, 1952 Y W, M BROBECK I 2,584,541

VARIABLE-SPEED TRANSMISSION Filed NOV. 24, 1947 3 Sheets-Sheet 2 Feb. 5, 1952 w. M. BROBECK VARIABLE-SPEED TRANSMISSION Filed NOV. 24. 1947 I 3 Sheets-Sheet 3 INVENTOR. wlLUAM M. BQOBECK Patented Feb. 5, 1952 UNITED STATES f PAi'ialxll -oEFicE i VARIABLE-SPEED 'raAN-sivussIoN William M. robecnfeferkeley, Calif. Application November 24, 1947, seria1No. 787,748 Y The present invention relates to variable speed transmissions, particularly to such transmissions which are operated Aby frictional contact between several-members whose radial relationships can be changed to vary the speed of the driven members. A f

' Friction contact variable speed transmissions have been useful in the accommodation of motors and engines lto applications requiring a variety of speedsand-power changed at the will of the operator's'uchas motor cars, machine tools, and Wherever controlled variations in speed are desired becausefof the infinite variation of speeds possible through the ranges for which the frictional contact membersare designed. Unfortunately, due to several seemingly characteristic disadvantages, they have neverv enjoyed Ipractical usage;

One of these disadvantageswas slippage between the driving andI driven members.. It is apparent that enough force'rnust.A be applied at the contact for operationat any givenr torque loading. On the other hand, where the Adriving and driven members are continuously forced into an extremely tighticontact in an attempt to overcome slippage, excessive wear and early failure of the contact surfaces is'producedwhich is as great a disadvantage as the slippage.

An object of this invention therefore is to provide a means for automatic -adjustment between the drivingand driven members of a friction contact transmission which will eliminate slippage and still not unduly submit the bearings and the rollers to continuous high stresses which materially shorten their lives. As described hereafter, this is accomplished by a mechanism which varies the friction contact with the torque load imposed upon the motor and driving member and produces only the contacting'force required to operate without slipping. -f

In the past one of the great difculties has been shifting of the driving and driven membersto the various `radial relationships necessary to accomplish the changes in speed. This difficulty limited the choice of surfaces availablefor contact members. In most friction transmissions the changing mechanism had to be forced against centrifugal or centripetal force, the power ofthe motor andthe axial friction of the members, with vconsequent strain -on both operator and equipment.

Thus it is an object also to provide a means of varying the relationship between driving and driven members in a frictionidrive transmission which will operate Aeasily andwithout burden 9 claims. (Crm1- 191) o'rqstrain upon'either the equipment or operator.

"Further, to provide-at the same-'time a speed changing-mechanism which will permit the use ofidrivin'g and driven members having convex and concaveA interacting 'surfaces for improved `friction contact.- v-f i.

iItvisamong the objects of this inventionto lprovideia device which combines the use of concav'eand convex coacting surfaces for frictional contact, a ,pressure rmeans .l limiting the l' intensityoflsaid frictional-contact.actuated by the torque Yof the vdriving end ofthe "transmission, and r`the replacement Lof conventional adjustmentvmechanism withv a unit which shifts the V'radial` relationships of the drivingand driven members without strain .regardless of whether thetransmission is in operationor at rest, under load or .-unloaded. The present invention makes it possible to adapt the great versatility of friction drive to applications such as automobiles, power tools, in fact anywhere where transmissions may `be used to advantage, due to the elimination of hitherto objectionable characteristics'.

FurtherV objects are to provide a construction of maximum simplicity, economy and ease of assembly and disassembly and such.further objects, advantages Yandcapabilities as' will ifully appear and as are inherently possessed ybyY the deviceiand invention ydescribed herein. i The invention further resides inthe combina.- tion, construction and arrangementof parts illustrated in the accompanying drawings and while there is'. shown thereinV a preferred embodiment, it is to be understood that the same is illustrativeV of the inventionand that the invention is capableof modification and other usesandl comprehends` other. details of construction without departingY fromA the ,spirit thereofor the scope ofthe appended claims. In'the accompanying drawings forming a part of this specicatioir and in which like numerals are employed tojdes'ignate.

like parts throughout the same: y

.the'line I--I of Figure 3, with a portion thereof shown-intop plan- View, Aof the unit showing among otherv things, the position of the friction contactcmembers andthe driving mechanism. g y

Figure 2 is a side elevationalview partly in vertical section taken on the line II--II of Figure 1, and looking in the direction of the' arrows, showing particularly the torque loading device. Figure` 3. is an end elevational view partly in,

Figure 1 is a. horizontal section view' taken on other vend by bearing IB.

vertical section taken on the line III- III of Figure 1 and looking in the direction of the arrows, showing the adjustment arrangement for the friction contact.

Figure 4 is a diagrammatic View illustrating the cam arrangement for shifting the position of the driven members to change speed, the posi-J tion shown being substantially the minimum ratio (highest gear), v

Referring nowspecically to the drawings and particularly 'to Figurel, input shaft II is driven by any power source such as an electric motor or any kind of engine. ries cam I2 which is splined thereto or secured in any other suitable manner so that it rotates with the shaft. The inturned edge lI2a. of cam I2 is cut with spaced depressions I2b (see Figure 2) in the bottoms of which are located balls I3.

The input shaft II car-` i A similar but oppositely disposed cam I4-isse cured to or formed integrally with the driving roller,.I5. The inner or driving roller I5 is supported atone .end by the cam I4 and 'at the Since the balls I3 are -held between thediamond shaped depressions `of the oppositely disposed cams I2 and I4 it is to be noted that as shaft II rotates in either direction it Will cause the balls I3 to roll on the cam 'faces and tend to` spread the cams apart against the, action of spring 59.l The shape of camslIZ and I4 is such that the spreading force .is at all timesproportional to the torque transmitted. Shaft II `is free to rotate independently of the driven roller I5 but is heldinengagement by the force caused from the cam I2 ,through the balls I3 to the cam I4. It is to be noted that the concave :curve of the roller I5 yrepresented by thecurve A-B is a true arc of a circle. Adjacent to the inner driving roller I5 are twin rollers I8, one at either side thereof, which are identical in every respect. The rollers I8 have a convex curved surface represented by the curve C-D and are .likewise true arcs of a circle but of smaller'fradiusthan that of the curve A-B. Bearing i8 supporting the inner roller I5 provides no axial restraint so that the axial mo- .Y

tion'of.' roller I5 produces .'acontacting force between the inner roller I5 and the two outer rollers I8." It is intended that the longitudinal axis of both the inner and outer rollers should lie in the same horizontal plane. The effect of the contact acting. upon'rollers I8 is to force each of them outwardly andat thesame time in an axial directionaiTheN axial, component, `of the force is carried Vthrough the main bearing I9, bearing housingV 2E),V rollers 2Ia (carried in the bearing housing 20 above and below the rollers I8) to thrust cams 22 mounted upon equalizing plate 23., :The radial components .ofthe contact be tween inner. roller I5 and outer rollers I8 are taken through bearings I9 and 24 bearing housings 26 and 26 and rollers 25 (carried by thebearing housings v26) to lower4 and upperY cam-*shifting plates 28 and 3B respectively. f

The lower and upper cam plates 28 and 30 are identical in Vsize and shape andare spaced above and below-'the inner and outer rollers I5 and I8. The shape of the cam `platesis clearly shown in the diagram of Figure 4. The came surface 51 which abuts rollers at the input end and rollers 2| at the output end can also be made a -true'arc of a circle.' The variable speed transmision portion of the device is contained within the housing 35. Within this housing the lower cam plate 28 is supported upon a butterfly shaped horizontal lplate carried on .shafts 49.

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3I having wing tips or tongues 33 which t into guides 34 in the wall of case 35. This permits slight movement of the plate 3I but only at right angles to the roller axis. The lower cam plate 23 is permitted to move horizontally and parallel to the axis of the rollers because of the key 32 in keyway 32a. Cam plate 28 is solidly connected to the upper cam plate 30 by side members 29 so that the movement between them is integral and identical. lThus cam'plates 28 and 38 are permitted to move axially and transversely but not to rotate.

The plate 3| supporting lower cam plate 28 and its uper counterpart, cam plate 38, is held in position at the base of the case 35 by supports 3asshown in Figures 2 and3. At the top .cam .plate l36 is held in position by depending supports 38a; the depending termini of which bear on the top surface of plate 38 directly above roller I5. To one end of the cam plate 38, preferably at the input end, is attached a screw 38 by means of pin 39 through the slot 82 in cam plate 30. Screw 38 passes through threaded bevel pinion 40 which meshes with pinion 4I carried on shaft-42 which is rotated by the handwheel 43. It is apparent that by the rotation of the handwheel 43 theupper cam plate v3l) is moved forward and backward vin a horizontal plane :and ysince :the lower cam plate 28 isvrigidly joined with the upper plate .30, an identical mo tion is made by the lower cam plate 28.V The purpose and function of thetwo integrallyconnected cam plates `is to equalize the force on thev two rollers I8.

Rollers I8 carry universal joints ,44 to which are connected shafts 45 and universal joints 46 The shafts 49 are free to slide axially inside gears 1418 but are prevented from turning with `respect "togears 48 by splines 49a. Byl locating universal joints 44 and 4B approximately equidistantto either side of the center 'of'rollers I8 andinzthe correct angular relation to each other, the variation in angular velocity introduced .by the action of the joints 44 and k46 can be largely cancelled out.

At the output end of the housing 5I contains a planetaryg'ear by which the ratio variation obtainable with rollers I5 and I8 can be changed to secure continuous variation from forward. through zero output speed to reverse. Alternately the output. could be taken from a single gear meshing with .both gears 48 omitting the extension 'of shaft II, through roller I5, if rotation .in only one :direction were desired.

As illustrated in the drawings, gears 48 drive gear 50 through idlers. which are not shown.

Gear 5I) is. positively connected to .internal gear 52. Gear v 53 is mounted on .the extension of shaft .I I. Shaft 54 carries spider 155 which in turn carries pinions 55. Since gear 53, .planet pinions 55 and internal gear 52 constitute `a planetary system,.the speed -of the shaft II may be combined with thespeedsof Vgear 58, as determined by the ratio obtained through the rollers I5 and I8, to `give overall :speed yvariations 'between shaft I I and shaft 5 4 from .forward through zero to reverse speeds.

The diagrammatic cam .arrangement shown in Figure f4 is the `type Vof system preferred for changing' the ratios between the speeds of driving roller I5 and driven rollers I8. The position of the rollers in Figure 1 :shows a contact point E which is substantiallya median point lbetween the area of minimum ratio, ai. e. as D approaches A, andthe/point of fmaximum. ratioVi. e. asv the -poi'nt C approaches B. Inorder to shift and accomplish changes infspeeds the handwheel 43 is rotated causing cam plates Vf3IIl and 28-.to movel .I8to approach each other and the. opposite ends to separate. As shown in Figure 4 the input end of roller I5 has beenfmoved sothat the contact point is substantially at F and is approaching the point of minimum ratio (highest gear), and the output ends have correspondingly separated in a horizontal plane. `:As .-a result of the movement the points of contact between the roller I5 and the rollers I8 move vtoward. one end, .and the -speed ratio changes vaccording to the radii ofthe roller I5 and the rollers I8 at the Vpoint of contact. Each change of contact throughout the entire length of the rollers will result .in adifferent gear. ratio in kboth directions of. rotation. As stated above cam surface 51 in both...cam plates 28 and 3i] canbe approximated byl true 'arcs of a circle. They are so calculated as to give a rook- .ing motion to theshifting of contact points with only a negligible amount of sliding motion. Cam surfaces 5l bear against the curved surface of rollers 2|. It will beobserved that asthe cam plate 30 shifts the ontact point from that shown in Figure `1 at E to; that shown at F in Figure a, the rollers 2I and 25 will rotate in a counterclockwise directionand vice versa when the cam plates are moved in the opposite direction. The

.rollers Zia, which are directly beneath rollers 2|,

bear against the curved surface of the thrust cams 22 mounted at the top and bottom of each of the two equalizing plates 23. The equalizing plates 23 are held against longitudinal movement bystops 60, the terminiv of which rest within grooves 6I cut in the face of equalizing plates 23. They are held against lateral movement by stops 62 which bear against the outer edge of the equalizer plates 23. Asy handwheel 43 isv moved, the plates 28 and 30 move longitudinally and cause therollers I8 to shift contact points with'respect to the roller I5 with substantially no sliding and very little axial motion of roller I5 occurs. This `makes it possible to change the ratio whether the rollers are running' at high' speed or stopped, and with or withoutload, with a minimum of effort applied at thehandwheel 43. While it has been disclosed herein that the'change of ratio may be accomplished by the rotation of handwheel 43 it is'apparent that the present invention contemplates the use of any other suitable means for moving the shifting cams and accomplishing this result. It is apparent that the unique means provided to vary the contacting force between the rollers I5 and I8 automatically as the load increases or decreases, is one ofthe prime advantages of this device. Thus, the contacting force between rollers I5 and I8 is governed'by the tangential force at the contact required to transmit the various ratios. This is so arranged that, except near zerol torque, the contacting force is alwaysmaintained at a constant ratio to theforce at'fwhich slipping would occurand the spring 55V maintains a small contacting force sufcien't to prevent the rollers separating at Zero torque.

This contact or Etangential pressure is Vproe duced by the wedging actionpf roller I5 moving axially between rollers I3. Cams I2 and I4 through balls* I3,.-coact"t`o produce an'axial force for moving roller` I5 proportional to :the torque carriedfby' shaft II.Y Coil spring 59 encircling shaftv IiI insidefthecasing 35 forcescam I2'away from the casing 35 and produces a small axial force sufficient to keep the rollers I5 and I8 from separating at zero torque. As the torque on the shaft increases a point is reached when the axial force between the cams I2 and I4 through rballs I3, becomes greater than that of spring 59 atwhich point cam I2 moves along the spline 63 on shaft II until it comes in contact with the spring retainer 54. At torque values above this point spring 59 has no effect and the axial force on cam I4 is directlyproportional to the torque acting upon it. v

The concave curve ofroller I5 shown in Figure 1 as the curve A-B is calculated so that the Lsine of angle 55 in Figure .4, between the radius ofthe roller` and a line perpendicular to a tangent at the point of contact, increases approximately in proportion to theradius. As practically applied, the

contour of roller I5 Acan be rmade an arc of a circle andthe sine of angle 55 can be proportional to the radius at any two points in the length of the roller, departing from proportional by only a few percent at the other points.

Inasmuch as the contact pressure which acts perpendicular to the surface of the rollers is proportioned to the axial force divided by the sine of the angle S5 and as the tangential force transniitted is proportional to the torque on rollers I8 divided by the radius and furthermore that through the action of cams I2 and I4 the axial force is proportional to the torque applied, it can be seen that the ratio of contact force to tangential force will be substantially constant at all ratios and torques greater than those necessary to compress springs 59.

In order to insure self-alignment of the rollers I 8, support plate SI is free to move at right angles to the axis of the rollers I5 and I8 to the extent that the tongues 33 are permitted to move in guides 34. Similar movement is accepted by the movement of pin 39 in slot 62. Accordingly, rollers I 3 are movable in a direction at right angles to the axis of roller I5 to prevent unbalance between the force on the opposite sides of roller I5, which might interfere with the action of cams I2 and I4.

Although the description-proceeds from the viewpoint that shaft II is the input shaft connected to a power source, it is to be understood that the same can be reversed and the power source connected to shaft 54. In this event shaft 54becomes the input shaft and shaft l I becomes the means for obtaining the overall speed variations in precisely the same manner as described.

Likewise it is to be understood that although balls I3 are shownand described any rolling elements will function in precisely the same way and are included herein. AAlso as described about the true arcs of circles referred to may be approximated without materially affecting the 0peration of the device.

I claim:

l. In a variable speed friction transmission a driving shaft operably connected to al source of rotating power, a first cam splined to said driving shaft, a driving roller operable to vary the contact lforce in proportion to the tangential force, the said driving roller having a longitudinal concave curved surface which curve is the true arc of a circle, a second cam integral with said driving roller' with its cam face opposed to the cam face of said first cam, a plurality of balls retained between the cam surfaces of said first andsecond cams for transmitting the motion from one to the other, a pair of Substantially identical driven rollers having their4 longitudinal axis inl substantially the same horizontal plane as that ofthe driving roller and having longitudinal convex curved surfaces the curve of which is the true arc of a circle, means operable in conjunction with the said rst and second cams for varying the contact force between said driving roller and said driven .rollers automatically as the load increases or decreases, an output shaft, and means for securing the effects of the operation of said contacting rollers cn the said output shaft.

2. In a variable speed friction transmission a driving shaft operably connected to a source of rotating power, a iirst cam splined to said driving shaft, a driving roller operable to vary'the contact force in proportion to the tangential force, the said driving roller having a longitudinal concave curved surface which curve is the 'true arc of acircle, a second cam integral with said driving roller with its cam face opposed to the cam face of said first cam, a plurality of balls retained between the cam surfaces of said first and second cams for transmitting the motion in conjunction with the said rst and second 5' cams for varying the contact force between said driving roller and said driven rollers automatically as the load increases or decreases, an output shaft, and means for securing the effects of the `operation of said contacting rollers on the said output shaft. j A

3. In a variable speed friction transmission a driving shaft operably connected to a source of rotating power, a rst cam splined to said driving shaft, a drivng rolleroperable to vary the contact force in proportion to the tangential force, the said driving rollei` having a longitudinal concave curved surface which curve is the true arc of a circle, a second cam integral with said driving. roller with its cam face opposed to the cam face of said rst cam, a plurality of balls retained between the cam surfaces of said first and second cams for transmitting thefmotion from `one to the other, a pair` of substantially identical driven rollers having their longitudinal axis in substantially the same horizontal plane as that of the driving roller and having longitudinal convex curved surfaces the curve of which is the true are of a circle, a pair of identically formed and moving cam plates for moving the contact points between said driving and driven rollers throughout their axial length :with a rocking motion to *Y accomplish speed ratio changes, means for moving said cam plates by which the contact point changes are effected,

means operable in conjunction with the said'V first and second cams for varying the contact force between said driving roller and said driven yrollers automatically as the load increases or decreases, an output shaft, and means for securing the effects of the operation of said contacting rollers on the said output shaft.

4. A variable speed friction transmission comconnected to a source of rotating power, a first -cam rotatable with said driving sha-ft, a driving roller operable to vary the contact force `in proportion to the tangential force, the said driving roller having a longitudinal concave curved surface which approximates a true Varc of a circle. a second cam rotatable with said driving roller having its cam face `opposed to the cam face of said first cam, a .plurality of rolling elements Vbetween the cam faces of said rst and second 'cams for transmitting Vthe motion from one to the other, av pair of Asubstantially identical driven rollers one on veither side of said driving roller and in contact therewith, all with their longitudinai axis in substantially the same horizon:- tal plane, having a longitudinal convex curved surface which'approximates a true yarc of a circle, means operable in conjunction with the said first and second cams for varying the contact force between said driving Vthe driven rollers re gardless' of the place of contact as the load increases or decreases, an output shaft, and means for securing the eiiectsof the operation of said contacting rollers on the output shaft.

5. A variable speed friction transmission comprising in combination a driving shaft operably connected to a source of rotating power, a first cam rotatable with said driving shaft, a driving roller operable to vary the contact force in proportion to the tangential force, the saidv driving roller having a longitudinal concave curved surface which approximates a true arc of acircle, a second cam rotatable with said driving roller having its cam face opposed to the cam face of said first cam, a plurality of rolling elements between the cam faces of said rst and second cams for transmitting the motion from one to the other, a pair of substantially identical driven rollers one on either side of said driving roller and in contact therewith, all with their longitudinal axis in substantially the same horizontal plane, having a longitudinal convex curved surface which approximates a true arc of a circle, means for moving the contact points between said rollers throughout their axial length to accomplish speed ratio changes, means operable in conjunction with the said first and second cams for varying the contact force between said driving and driven rollers regardless of the place of contactas the load increases or decreases, an output shaft, and means for securing the effects of the operation of said contacting rollers on the output shaft. Y

6. A variable speed friction transmission comprising in combination a driving shaft operably connected to a source ofrotating power, a first cam rotatable with said driving shaft, a driving roller operable to vary the contact force in proportion to the tangential force, the said driving roller having a longitudinal concave curved surface which approximates a true arc of a circle. a second cam rotatable with said driving roller having its cam face opposed to the cam face of said first cam, a plurality of rolling elements between the cam faces of said first and second cams for transmitting the motion from one to the other, a pair of substantially identical driven rollers one on either side of Asaid driving roller and vin contact therewith, all with their longitudinal axis in substantially the same horizontal plane, having a longitudinalconvexy curved surface which approximates a trueV arc of a circle, a pair of identically vformed and moving cam prising in conibination a driving shaft operably 'Il plates for moving the contact points between said rollers throughout their axial length with a rocking motion, to accomplish speed ratio changes, means for moving said cam plates by which the contact point changes are effected. means operable in conjunction with the said first and second cams for varying the contact force between said driving and driven rollers regardless of the place of contact as the load increases or decreases, an output shaft, and means for securing the eiects of the operation of said contacting rollers on the output shaft.

7. A variable speed transmission comprising co-operable, oppositely tapered, rst and second rollers arranged to be in tangential, rolling contact with each other, at least one of said rollers being mounted for shifting axially with respect to the other roller to Vary the speed ratio therebetween, the surface of one roller being convex and the surface of the other roller being concave, said surfaces being so developed that the sine of the angle included between a radius of the concave roller and a line perpendicular to a tangent at the point of contact of the rollers varies approximately in proportion to said radius at the point of contact.

8. A variable speed transmission comprising cooperable, oppositely tapered, first and second rollers arranged to be in tangential, rolling contact with each other, at least one of said rollers being mounted for shifting axially to vary the speed ratio therebetween, one of said rollers having a convex surface and the other of the said rollers having a concave surface developed as an arc of a circle, the said contacting surfaces being so developed that the sine of the angle included between a radius of the concave roller and a line perpendicularto a tangent at the point lof contact is proportional to the radius of the concave roller at any two selected points along the length of said concave roller and departs from such proportionality by only a small amount at other points along the length of said concave roller.

9. A torque loading device of the character; described comprising co-axial, rotatable driving and driven members, a rst cam means fixed to the driven member, a second cam means slidably but non-rotatably mounted on the driving member, yieldable means urging said second cam means towards said first cam means, said rst and second cam means cut with oppositely disposed spaced depressions and means disposed in said spaced depressions between said cam members and supported thereby for transmitting motion of said second cam member to said rst cam member.

Y WILLIAM M. BROBECK.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,097,007 Weisel Oct. 26, 1937 2,125,998 Erban Aug. 9, 1938 2,252,630 Heer Aug. 12, 1941 FOREIGN PATENTS Number l Country Date 446,325 France Sept. 30, 1912 

